1. Field of the Invention
This invention relates to holography, and more particularly to an improved apparatus for producing holographic motion pictures.
2. Description of the Prior Art
Since the resurgency of holography in 1962, there has been the desire to devise a holographic motion picture camera which would produce true three-dimensional images of a moving target in real time with resolution of front surface details. Such would also allow single-exposure holograms of fast-moving objects and transient events. The primary drawback to the development of such a device has been the very nature of the holographic process itself. The two beams necessary to record a hologram (the object and reference beams, respectively) must stay in phase one with respect to the other by less than a half wave length of the radiation being used to record the hologram. In illuminating the front of an object which is moving during a holographic exposure, it is thus necessary that the phase shift in the object beam during this exposure be kept within this limit. This is true since phase of the radiation is a constant times the magnitude of the change in the object beam path length. Consequently, if the object moves during the exposure, then the phase of the object beam changes by a constant times the magnitude of the change in the object beam path length, due to the object's total motion or displacement during exposure.
In a previous patent application (now U.S. Pat. No. 3,752,556), the applicant disclosed a holographic motion picture camera which has successfully obtained three-dimensional motion pictures. Its success is due primarily to the use of a unique elliptical holographic arrangement which partially relaxes or decouples the motion or displacement of the object from the phase change in the optical path length of the object beam. It accomplishes this through the constancy properties of the ellipse. This device does, however, have limitations because of the allowable magnitude of total motion of the object during the hologram exposure.
It is the purpose of this invention to further relax, decouple, or compensate for the motion or displacement of the object from the phase change of the optical path length of the object beam, and thus to enable the camera to record images of objects moving at greater speeds, i.e., or over longer distances during exposure.